- add support for native recursive mutexes (pthread and Win32) and remove
  not satisfactory generic recursive implementation.
- remove support for older pthread versions (PthreadDraftVersion < 10),
  all modern systems support version 10 now.


git-svn-id: http://root.cern.ch/svn/root/trunk@29797 27541ba8-7e3a-0410-8455-c3a389f83636